1.1.1.5 Class 4 – Conditional State Transition and Conditional State Output (Mealy State Machine)

Class 4 state machines are the most general type of state machine, where both the next-state, $X$, and the outputs, $I$, are determined by the present state and the inputs, $Q$. The portion of the general state machine relevant to Class 4 is shown with solid lines in Figure 1-6.

Unlike Class 3 state machines, where one state can produce only one output, Class 4 state machines allow one state to produce several different outputs as a function of the inputs. This capability often allows an algorithm to be described with fewer states as compared to Class 3 state machines.

The Class 4 state machine is more commonly known as the Mealy State Machine. The output and next-state expressions can be represented as follows:

$X\leftarrow g[X,Q]$

$I=f[X,Q]$